1. Field of the Invention
The invention relates to a device for inductively heating flat metal materials, e.g. strips and plates, with at least one pair of induction coils which form a gap through which the material can pass, whereby the induction coils have an iron core made up of transformer stampings with grooves in which current conductors are located, at least some of which can be switched independently.
2. Description of Related Art
Each induction coil consists of an iron core with a series of grooves in which the current conductors of the induction coils are embedded. These current conductors run crossways to or in the direction of motion of the material. Uniform heating across the entire width of the material is always a problem with this type of inductive heating device, in particular when the device is required to work with materials of various widths.
In order to provide better uniform heating of flat metal materials of various widths, EP-PS 0 150 793 proposes that the induction coil be divided into several induction coil sections arranged side-by-side in a longitudinal direction, each with its own induction winding and its own magnetic field. The distance of the induction coil sections from one another can be altered or adjusted to comply with various material widths. In addition, electrical means are provided to control the electrical current intensity in the induction coil windings. Adjustment to suit various material widths is by means of switching the outermost induction coil sections on or off. This known device allows adjustment of the heating energy to suit various material widths. However, because of the large number of induction coil sections arranged separately from one another, assembly of the device is extremely time consuming. In addition, the almost square spools result in large pole widths which are unfavourable in terms of temperature distribution.
A further disadvantage of this known device is a poor groove filling factor. In addition, the conductor sections running vertically to the direction of transport cause overheating of the edges of the material. Exact adjustment to the width of the material is not possible. Relatively high heating of the iron core sections is also unavoidable, as conductor sections run parallel to the iron core layers.
In DE-PS 884 811, an inductive heating device for the uniform heating of flat metal materials is described which has two or more inductive heat conductors arranged one behind the other in the direction of motion and curved in an undulating fashion, which are located singly or in multiple form staggered in relation to one another. An essential disadvantage of this known device lies in fact that although uniform heating may be achieved for one particular width of material, a satisfactorily uniform heating of other widths of material is no longer possible.